Resin based post rinse for improved throwpower of electrodepositable coating compositions on pretreated metal substrates

ABSTRACT

Disclosed are methods for treating metal substrates, including ferrous substrates, such as cold rolled steel and electrogalvanized steel. The methods include (a) contacting the substrate with a pretreatment composition including a group IIIB or IVB metal and an electropositive metal, (b) contacting the substrate with a post rinse composition and (c) electrophoretically depositing an electrodepositable coating composition to the substrate, wherein the post rinse composition improves the throwpower of the subsequently applied electrodepositable coating composition. The present invention also relates to coated substrates produced thereby.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a divisional of U.S. patent application Ser.No. 13/323,926 filed Dec. 13, 2011, entitled: “RESIN BASED POST RINSEFOR IMPROVED THROWPOWER OF ELECTRODEPOSITABLE COATING COMPOSITIONS ONPRETREATED METAL SUBSTRATES” incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with Government support under Contract No.W15QKN-07-C-0048 awarded by the ARDEC. The United States Government mayhave certain rights in this invention.

FIELD OF THE INVENTION

The present invention relates to methods for coating a metal substrate,including ferrous substrates, such as cold rolled steel andelectrogalvanized steel. The present invention also relates to coatedmetal substrates.

BACKGROUND INFORMATION

The use of protective coatings on metal substrates for improvedcorrosion resistance and paint adhesion is common Conventionaltechniques for coating such substrates include techniques that involvepretreating the metal substrate with a phosphate conversion coating andchrome-containing rinses. The use of such phosphate and/orchromate-containing compositions, however, imparts environmental andhealth concerns. As a result, chromate-free and/or phosphate-freepretreatment compositions have been developed. Such compositions aregenerally based on chemical mixtures that in some way react with thesubstrate surface and bind to it to form a protective layer. Forexample, pretreatment compositions based on a group IIIB or IVB metalcompound have recently become more prevalent.

After pretreating the substrates with pretreatment compositions, it isalso common to subsequently contact the pretreated substrates with anelectrodepositable coating composition. Both cationic and anionicelectrodepositions are used commercially, with cationic being moreprevalent in applications desiring a high level of corrosion protection.As with all electrodepositable coating compositions, it is highlydesirable to increase their respective throwpowers to allow theelectrodepositable coating compositions to be deposited in recessedareas of the pretreated substrates without otherwise adversely affectingthe performance characteristics of the coated substrates.

SUMMARY OF THE INVENTION

In certain respects, the present invention is directed to a method fortreating a metal substrate comprising: (a) contacting the substrate witha pretreatment solution comprising a group IIIB and/or IVB metal and anelectropositive metal; (b) contacting the substrate with an anionicresin-based post rinse composition; and (c) electrophoreticallydepositing a cationic electrodepositable coating composition onto thesubstrate.

In still other respects, the present invention is directed to methodsfor treating a metal substrate comprising contacting the substrate (a)contacting the substrate with a pretreatment solution comprising a groupIIIB and/or IVB metal and an electropositive metal; (b) contacting thesubstrate with an cationic resin-based post rinse composition; and (c)electrophoretically depositing an anionic electrodepositable coatingcomposition onto the substrate.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities ofingredients used in the specification and claims are to be understood asbeing modified in all instances by the term “about”. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Inaddition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances.

As previously mentioned, certain embodiments of the present inventionare directed to methods for treating a metal substrate. Suitable metalsubstrates for use in the present invention include those that are oftenused in the assembly of automotive bodies, automotive parts, and otherarticles, such as small metal parts, including fasteners, i.e., nuts,bolts, screws, pins, nails, clips, buttons, and the like. Specificexamples of suitable metal substrates include, but are not limited to,cold rolled steel, hot rolled steel, steel coated with zinc metal, zinccompounds, or zinc alloys, such as electrogalvanized steel, hot-dippedgalvanized steel, galvanealed steel, and steel plated with zinc alloy.Also, aluminum alloys, aluminum plated steel and aluminum alloy platedsteel substrates may be used. Other suitable non-ferrous metals includecopper and magnesium, as well as alloys of these materials. Moreover,the bare metal substrate being coating by the methods of the presentinvention may be a cut edge of a substrate that is otherwise treatedand/or coated over the rest of its surface. The metal substrate coatedin accordance with the methods of the present invention may be in theform of, for example, a sheet of metal or a fabricated part.

The substrate to be treated in accordance with the methods of thepresent invention may first be cleaned to remove grease, dirt, or otherextraneous matter. This is often done by employing mild or strongalkaline cleaners, such as are commercially available and conventionallyused in metal pretreatment processes. Examples of alkaline cleanerssuitable for use in the present invention include Chemkleen 163,Chemkleen 177, and Chemkleen 490MX, each of which are commerciallyavailable from PPG Industries, Inc. Such cleaners are often followedand/or preceded by a water rinse.

As previously indicated, certain embodiments of the present inventionare directed to methods treating a metal substrate that comprisecontacting the metal substrate with a pretreatment compositioncomprising a group IIIB and/or IVB metal. As used herein, the term“pretreatment composition” refers to a composition that upon contactwith the substrate reacts with and chemically alters the substratesurface and binds to it to form a protective layer.

Often, the pretreatment composition comprises a carrier, often anaqueous medium, so that the composition is in the form of a solution ordispersion of a group IIIB or IVB metal compound in the carrier. Inthese embodiments, the solution or dispersion may be brought intocontact with the substrate by any of a variety of known techniques, suchas dipping or immersion, spraying, intermittent spraying, dippingfollowed by spraying, spraying followed by dipping, brushing, orroll-coating. In certain embodiments, the solution or dispersion whenapplied to the metal substrate is at a temperature ranging from 60 to150° F. (15 to 65° C.). The contact time is often from 10 seconds tofive minutes, such as 30 seconds to 2 minutes.

As used herein, the term “group IIIB and/or IVB metal” refers to anelement that is in group IIIB or group IVB of the CAS Periodic Table ofthe Elements as is shown, for example, in the Handbook of Chemistry andPhysics, 63^(rd) edition (1983). Where applicable, the metal themselvesmay be used. In certain embodiments, a group IIIB and/or IVB metalcompound is used. As used herein, the term “group IIIB and/or IVB metalcompound” refers to compounds that include at least one element that isin group IIIB or group IVB of the CAS Periodic Table of the Elements.

In certain embodiments, the group IIIB and/or IVB metal compound used inthe pretreatment composition is a compound of zirconium, titanium,hafnium, yttrium, cerium, or a mixture thereof. Suitable compounds ofzirconium include, but are not limited to, hexafluorozirconic acid,alkali metal and ammonium salts thereof, ammonium zirconium carbonate,zirconyl nitrate, zirconium carboxylates and zirconium hydroxycarboxylates, such as hydrofluorozirconic acid, zirconium acetate,zirconium oxalate, ammonium zirconium glycolate, ammonium zirconiumlactate, ammonium zirconium citrate, and mixtures thereof. Suitablecompounds of titanium include, but are not limited to, fluorotitanicacid and its salts. A suitable compound of hafnium includes, but is notlimited to, hafnium nitrate. A suitable compound of yttrium includes,but is not limited to, yttrium nitrate. A suitable compound of ceriumincludes, but is not limited to, cerous nitrate.

In certain embodiments, the group IIIB and/or IVB metal compound ispresent in the pretreatment composition in an amount of at least 10 ppmmetal, such as at least 100 ppm metal, or, in some cases, at least 150ppm metal. In certain embodiments, the group IIIB and/or IVB metalcompound is present in the pretreatment composition in an amount of nomore than 5000 ppm metal, such as no more than 300 ppm metal, or, insome cases, no more than 250 ppm metal. The amount of group IIIB and/orIVB metal in the pretreatment composition can range between anycombination of the recited values inclusive of the recited values.

In certain embodiments, the pretreatment composition also comprises anelectropositive metal. As used herein, the term “electropositive metal”refers to metals that are more electropositive than the metal substrate.This means that, for purposes of the present invention, the term“electropositive metal” encompasses metals that are less easily oxidizedthan the metal of the metal substrate. As will be appreciated by thoseskilled in the art, the tendency of a metal to be oxidized is called theoxidation potential, is expressed in volts, and is measured relative toa standard hydrogen electrode, which is arbitrarily assigned anoxidation potential of zero. The oxidation potential for severalelements is set forth in the table below. An element is less easilyoxidized than another element if it has a voltage value, E*, in thefollowing table, that is greater than the element to which it is beingcompared.

Element Half-cell reaction Voltage, E* Potassium K⁺ + e → K −2.93Calcium Ca²⁺ + 2e → Ca −2.87 Sodium Na⁺ + e → Na −2.71 Magnesium Mg²⁺ +2e → Mg −2.37 Aluminum Al³⁺ + 3e → Al −1.66 Zinc Zn²⁺ + 2e → Zn −0.76Iron Fe²⁺ + 2e → Fe −0.44 Nickel Ni²⁺ + 2e → Ni −0.25 Tin Sn²⁺ + 2e → Sn−0.14 Lead Pb²⁺ + 2e → Pb −0.13 Hydrogen 2H⁺ + 2e → H₂ −0.00 CopperCu²⁺ + 2e → Cu 0.34 Mercury Hg₂ ²⁺ + 2e → 2Hg 0.79 Silver Ag⁺ + e → Ag0.80 Gold Au³⁺ + 3e → Au 1.50

Thus, as will be apparent, when the metal substrate comprises one of thematerials listed earlier, such as cold rolled steel, hot rolled steel,steel coated with zinc metal, zinc compounds, or zinc alloys, hot-dippedgalvanized steel, galvanealed steel, steel plated with zinc alloy,aluminum alloys, aluminum plated steel, aluminum alloy plated steel,magnesium and magnesium alloys, suitable electropositive metals fordeposition thereon in accordance with the present invention include, forexample, nickel, copper, silver, and gold, as well mixtures thereof.

In certain embodiments, the source of electropositive metal in thepretreatment composition is a water soluble metal salt. In certainembodiments of the present invention, the water soluble metal salt is awater soluble copper compound. Specific examples of water soluble coppercompounds, which are suitable for use in the present invention include,but are not limited to, copper cyanide, copper potassium cyanide, coppersulfate, copper nitrate, copper pyrophosphate, copper thiocyanate,disodium copper ethylenediaminetetraacetate tetrahydrate, copperbromide, copper oxide, copper hydroxide, copper chloride, copperfluoride, copper gluconate, copper citrate, copper lauroyl sarcosinate,copper formate, copper acetate, copper propionate, copper butyrate,copper lactate, copper oxalate, copper phytate, copper tartarate, coppermalate, copper succinate, copper malonate, copper maleate, copperbenzoate, copper salicylate, copper aspartate, copper glutamate, copperfumarate, copper glycerophosphate, sodium copper chlorophyllin, copperfluorosilicate, copper fluoroborate and copper iodate, as well as coppersalts of carboxylic acids in the homologous series formic acid todecanoic acid, copper salts of polybasic acids in the series oxalic acidto suberic acid, and copper salts of hydroxycarboxylic acids, includingglycolic, lactic, tartaric, malic and citric acids.

When copper ions supplied from such a water-soluble copper compound areprecipitated as an impurity in the form of copper sulfate, copper oxide,etc., it may be preferable to add a complexing agent that suppresses theprecipitation of copper ions, thus stabilizing them as a copper complexin the solution.

In certain embodiments, the copper compound is added as a copper complexsalt such as K₃Cu(CN)₄ or Cu-EDTA, which can be present stably in thecomposition on its own, but it is also possible to form a copper complexthat can be present stably in the composition by combining a complexingagent with a compound that is difficultly soluble on its own. Examplesthereof include a copper cyanide complex formed by a combination of CuCNand KCN or a combination of CuSCN and KSCN or KCN, and a Cu-EDTA complexformed by a combination of CuSO₄ and EDTA.2Na.

With regard to the complexing agent, a compound that can form a complexwith copper ions can be used; examples thereof include inorganiccompounds, such as cyanide compounds and thiocyanate compounds, andpolycarboxylic acids, and specific examples thereof includeethylenediaminetetraacetic acid, salts of ethylenediaminetetraaceticacid, such as dihydrogen disodium ethylenediaminetetraacetate dihydrate,aminocarboxylic acids, such as nitrilotriacetic acid and iminodiaceticacid, oxycarboxylic acids, such as citric acid and tartaric acid,succinic acid, oxalic acid, ethylenediaminetetramethylenephosphonicacid, and glycine.

In certain embodiments, the electropositive metal, such as copper, isincluded in the pretreatment compositions in an amount of at least 1ppm, such as at least 5 ppm, or in some cases, at least 10 ppm of totalmetal (measured as elemental metal). In certain embodiments, theelectropositive metal is included in such pretreatment compositions inan amount of no more than 500 ppm, such as no more than 100 ppm, or insome cases, no more than 50 ppm of total metal (measured as elementalmetal). The amount of electropositive metal in the pretreatmentcomposition can range between any combination of the recited valuesinclusive of the recited values.

In some embodiments, the pretreatment composition may be a silane or anon-crystalline phosphate, such as iron phosphate, containingpretreatment composition. Suitable silane containing pretreatmentcompositions include, but are not limited to, certain commerciallyavailable products, such as Silquest A-1100 Silane, which is describedin the Examples herein and which is commercially available fromMomentive Performance Materials. Suitable non-crystalline phosphatecontaining pretreatment composition include pretreatment compositionthat comprise, iron phosphate, manganese phosphate, calcium phosphate,magnesium phosphate, cobalt phosphate, or an organophosphate and/ororganophosphonate, such as is disclosed in U.S. Pat. Nos. 5,294,265 atcol. 1, line 53 to col. 3, line 12 and 5,306,526 at col. 1, line 46 tocol. 3, line 8, the cited portions of which being incorporated herein byreference. Suitable non-crystalline phosphate containing pretreatmentcompositions are commercially available, such as Chemfos® 158 andChemfos® 51, which are iron phosphate pretreatment compositionscommercially available from PPG Industries, Inc.

In certain embodiments, the pretreatment composition comprises aresinous binder. Suitable resins include reaction products of one ormore alkanolamines and an epoxy-functional material containing at leasttwo epoxy groups, such as those disclosed in U.S. Pat. No. 5,653,823. Insome cases, such resins contain beta hydroxy ester, imide, or sulfidefunctionality, incorporated by using dimethylolpropionic acid,phthalimide, or mercaptoglycerine as an additional reactant in thepreparation of the resin. Alternatively, the reaction product is that ofthe diglycidyl ether of Bisphenol A (commercially available from ShellChemical Company as EPON 880), dimethylol propionic acid, anddiethanolamine in a 0.6 to 5.0:0.05 to 5.5:1 mole ratio. Other suitableresinous binders include water soluble and water dispersible polyacrylicacids as disclosed in U.S. Pat. Nos. 3,912,548 and 5,328,525; phenolformaldehyde resins as described in U.S. Pat. Nos. 5,662,746; watersoluble polyamides such as those disclosed in WO 95/33869; copolymers ofmaleic or acrylic acid with allyl ether as described in Canadian patentapplication 2,087,352; and water soluble and dispersible resinsincluding epoxy resins, aminoplasts, phenol-formaldehyde resins,tannins, and polyvinyl phenols as discussed in U.S. Pat. No. 5,449,415.

In these embodiments of the present invention, the resinous binder ispresent in the pretreatment composition in an amount of 0.005 percent to30 percent by weight, such as 0.5 to 3 percent by weight, based on thetotal weight of the ingredients in the composition.

In other embodiments, however, the pretreatment composition issubstantially free or, in some cases, completely free of any resinousbinder. As used herein, the term “substantially free”, when used withreference to the absence of resinous binder in the pretreatmentcomposition, means that any resinous binder is present in thepretreatment composition in an amount of less than 0.005 percent byweight. As used herein, the term “completely free” means that there isno resinous binder in the pretreatment composition at all.

The pretreatment composition may optionally contain other materials,such as nonionic surfactants and auxiliaries conventionally used in theart of pretreatment. In an aqueous medium, water dispersible organicsolvents, for example, alcohols with up to about 8 carbon atoms, such asmethanol, isopropanol, and the like, may be present; or glycol etherssuch as the monoalkyl ethers of ethylene glycol, diethylene glycol, orpropylene glycol, and the like. When present, water dispersible organicsolvents are typically used in amounts up to about ten percent byvolume, based on the total volume of aqueous medium.

Other optional materials include surfactants that function as defoamersor substrate wetting agents, such as those materials and amountsdescribed earlier with respect to the plating solution.

In certain embodiments, the pretreatment composition also comprises areaction accelerator, such as nitrite ions, nitro-group containingcompounds, hydroxylamine sulfate, persulfate ions, sulfite ions,hyposulfite ions, peroxides, iron (III) ions, citric acid ironcompounds, bromate ions, perchlorinate ions, chlorate ions, chloriteions as well as ascorbic acid, citric acid, tartaric acid, malonic acid,succinic acid and salts thereof. Specific examples of suitable materialsand their amounts are described in United States Patent ApplicationPublication No. 2004/0163736 A1 at [0032] to [0041], the cited portionof which being incorporated herein by reference.

In certain embodiments, the pretreatment composition also comprises afiller, such as a siliceous filler. Non-limiting examples of suitablefillers include silica, mica, montmorillonite, kaolinite, asbestos,talc, diatomaceous earth, vermiculite, natural and synthetic zeolites,cement, calcium silicate, aluminum silicate, sodium aluminum silicate,aluminum polysilicate, alumina silica gels, and glass particles. Inaddition to the siliceous fillers other finely divided particulatesubstantially water-insoluble fillers may also be employed. Examples ofsuch optional fillers include carbon black, charcoal, graphite, titaniumoxide, iron oxide, copper oxide, zinc oxide, antimony oxide, zirconia,magnesia, alumina, molybdenum disulfide, zinc sulfide, barium sulfate,strontium sulfate, calcium carbonate, and magnesium carbonate.

As indicated, in certain embodiments, the pretreatment composition issubstantially or, in some cases, completely free of chromate and/orheavy metal phosphate. As used herein, the term “substantially free”when used in reference to the absence of chromate and/or heavy metalphosphate, such as zinc phosphate, in the pretreatment composition meansthat these substances are not present in the composition to such anextent that they cause a burden on the environment. That is, they arenot substantially used and the formation of sludge, such as zincphosphate, formed in the case of using a treating agent based on zincphosphate, is eliminated.

Moreover, in certain embodiments, the pretreatment composition issubstantially free, or, in some cases, completely free of any organicmaterials. As used herein, the term “substantially free”, when used withreference to the absence of organic materials in the composition, meansthat any organic materials are present in the composition, if at all, asan incidental impurity. In other words, the presence of any organicmaterial does not affect the properties of the composition. As usedherein, the term “completely free” means that there is no organicmaterial in the composition at all.

In certain embodiments, the film coverage of the residue of thepretreatment coating composition generally ranges from 1 to 1000milligrams per square meter (mg/m²), such as 10 to 400 mg/m². Thethickness of the pretreatment coating can vary, but it is generally verythin, often having a thickness of less than 1 micrometer, in some casesit is from 1 to 500 nanometers, and, in yet other cases, it is 10 to 300nanometers.

Following contact with the pretreatment solution, the substrate may berinsed with water and dried.

Next, after the pretreatment step, the substrate is contacted with aresin-based post-rinse solution. It has been surprisingly discoveredthat the use of a post-rinse, in conjunction with the use of anelectropositive metal such as copper in the pretreatment solution,increases the throwpower of subsequently applied electrodepositioncoatings as compared with the application of the electrodepositioncoatings applied to the substrate in the absence of the post-rinse.

As defined herein, the ability for an electrodepositable coatingcomposition to coat interior recesses of a substrate, at a giventemperature and voltage, is called “throwpower”. A higher “throwpower”means that the electrodepositable coating composition is further“thrown” into the recesses of a recessed substrate. Higher throwpowertherefore is synonymous with greater surface coverage on hard to reachrecessed areas of a substrate.

Moreover, the use of a post-rinse, as described in the previousparagraphs in conjunction with the use of an electropositive metal suchas copper in the pretreatment solution, does not adversely affect thecorrosion resistance of the formed panels.

In the context of the present invention, throwpower was evaluated byplacing two 4″×12″ pretreated and post-rinsed panels on either side of a4 mm shim and clamping them together. The shimmed panels were thenimmersed 27 cm into the electrocoat bath (either a cationic or anionicelectrodepositable coating composition bath) and coated to apredetermined thickness. Throwpower readings were recorded as apercentage by measuring the distance (in cm) from the bottom of the backside of the panels to the point where no coating was deposited anddividing that number by 27 cm.

In certain embodiments utilizing a resin based post rinse, thethrowpower for the immersion applied electrodepositable coatingcomposition increased at least 6% as compared to the throwpower of thesame electrodepositable coating composition applied to the substrateunder the same coating conditions in the absence of the post rinse step.

The type of resin-based post rinse utilized is dependent upon the typeof electrodepositable coating composition that is subsequently appliedto the treated substrate. For pretreated substrates to be coated with acationically applied electrodeposition coating, the resin-basedpost-rinse composition is anionic in nature (i.e. an “anionicresin-based post rinse composition”). Conversely, for pretreatedsubstrates to be coated with an anionically applied electrodepositioncoating, the resin-based post-rinse composition is cationic in nature(i.e. a “cationic resin-based post rinse composition”).

In certain embodiments, the resin-based post rinse solution is formed bydissolving a respective cationic or an anionic resin in water. Incertain of these embodiments, the resin solids of the resin-based postrinse solution is from 0.1 to 10%.

In certain embodiments, the pH of the anionic resin-based post rinsesolution is from 1 to 10, such as from 1 to 7.

In certain embodiments, the pH of the cationic resin-based post rinsesolution is from 6 to 14.

In certain embodiments, the cationic or anionic resin-based post rinsecomposition is applied to the pretreated panel by immersing thepretreated panel into the composition for a predetermined period oftime, such as, for example, 1 minute, removing the panel, rinsing withdeionized water, and drying the panel prior to application of an anionicelectrodepositable coating composition.

In certain other embodiments, the cationic resin-based post rinsecomposition is applied to the pretreated panel via a dry-in-placeapplication. In these embodiments, the composition is sprayed onto thepanel and dried without a rinsing step prior to application of acationic electrodepositable coating composition.

In another exemplary embodiment, the anionic resin-based post rinsecomposition comprises a phosphitized epoxy resin composition. Exemplarywater-based phosphitized epoxy resins that may be utilized includeNupal® 435 F and Nupal 510® R, both commercially available from PPGIndustries, Inc.

In certain of these embodiments, the water-based phosphitized epoxycomposition has a pH adjusted between 3 and 7. In certain otherembodiments, the resin content of the water-based phosphitized epoxycomposition is from about 0.1 to 10% resin solids.

In one exemplary embodiment, the cationic resin-based post rinsecomposition comprises an epoxy-functional material that is reacted witheither an alkanolamine, or a mixture of alkanolamines. In certainembodiments, primary or secondary alkanolamines, or mixtures thereof areused. Tertiary alkanolamines or mixtures thereof are also suitable, butthe reaction conditions differ when these materials are used.Consequently, tertiary alkanolamines are not typically mixed withprimary or secondary alkanolamines.

In certain embodiments, the alkanolamines have alkanol groups containingfewer than about 20 carbon atoms, such as fewer than about 10 carbonatoms. Examples of suitable alkanolamines include methyl ethanolamine,ethylethanolamine, diethanolamine, methylisopropanolamine,ethylisopropanolamine, diisopropanolamine, monoethanolamine, anddiisopropanolamine and the like.

In certain embodiments, the tertiary alkanolamines that may be usedcontain two methyl groups. An example of suitable material isdimethylethanolamine.

In certain embodiments, the epoxy-functional material and thealkanolamines are reacted in a equivalent ratio of from about 5:1 toabout 1:4, such as from about 2:1 to about 1:2.

The epoxy-functional material and the alkanolamines can be co-reacted byany of the methods well known to those skilled in the art of polymersynthesis, including solution, emulsion, suspension or dispersionpolymerization techniques. In the simplest cases, the alkanolamine isadded to the epoxy-functional material at a controlled rate, and theyare simply heated together, usually with some diluent, at a controlledtemperature. In certain embodiments, the reaction is conducted under anitrogen blanket or another procedure known to those skilled in the artfor reducing the presence of oxygen during the reaction.

The diluent serves to reduce the viscosity of the reaction mixture.Exemplary diluents are water-dispersible organic solvents. Examplesinclude alcohols with up to about eight carbon atoms, such as methanolor isopropanol, and the like; or glycol ethers such as the monoalkylethers of ethylene glycol, diethylene glycol, or propylene glycol, andthe like. Water is also a suitable diluent.

Other suitable diluents include nonreactive oligomeric or polymericmaterials with a viscosity ranging from about 20 centipoise to about1,000 centipoise, as measured with a Brookfield viscometer at about 72°F.; and a glass transition temperature lower than about 35° C., asmeasured by any of the common thermal analytical methods well known bythose skilled in the art. Examples include plasticizers such as tributylphosphate, dibutyl maleate, butyl benzyl phthalate, and the like knownto those skilled in the art; and silane compounds such as vinyltrimethoxy silane, gamma-methacryloxypropyl trimethoxy silane, and thelike known to those skilled in the art. Mixtures of any of thesealternative diluents, water, or organic solvents are suitable as well.

If a tertiary alkanolamine is used, a quaternary ammonium compound isformed. In this case, it is the usual practice to add all the rawmaterials to the reaction vessel at once and heat them together, usuallywith some diluent, at a controlled temperature. Typically, some acid ispresent, which serves to ensure that a quaternary ammonium salt isformed instead of a quaternary ammonium oxide. Examples of suitableacids are carboxylic acids such as lactic acid, citric acid, adipicacid, and the like. Acetic acid is preferred. The quaternary ammoniumsalts are preferred because these are more easily dispersed in water,and because they produce an aqueous dispersion with a pH in or near thedesired range. If, instead, a quaternary ammonium oxide is prepared, itcan later be converted to a quaternary ammonium salt with the additionof acid.

The molecular weight of epoxy-functional material that is reacted witheither an alkanolamine is limited only by its dispersibility in theother materials comprising the non-chrome post-rinse composition. Thedispersibility is determined, in part, by the nature of theepoxy-functional material, the nature of the alkanolamine, and theequivalent ratio in which the two are reacted. Typically, theepoxy-functional material that is reacted with either an alkanolaminehas a number-average molecular weight of up to about 1500, as measuredby gel permeation chromatography using polystyrene as a standard.

Optionally, the epoxy-functional material that is reacted with either analkanolamine can be neutralized to promote good dispersion in an aqueousmedium. Typically, this is accomplished by adding some acid. Examples ofsuitable neutralizing acids include lactic acid, phosphoric, aceticacid, and the like known to those skilled in the art.

The epoxy-functional material that is reacted with either analkanolamine is present in the cationic post-rinse composition at alevel of at least about 100 ppm, such as from about 400 ppm to about1400 ppm, the concentration based on the solid weight of theepoxy-functional material that is reacted with either an alkanolamine onthe total weight of the cationic post-rinse composition.

In a related embodiment, the cationic resin-based post rinse comprisesan amine adduct of Epon® 828 that may be formed as the reaction productof diethanolamine and Epon® 828, and in certain embodiments may be madein accordance with the method disclosed in Example 1 of U.S. Pat. No.5,653,823 (without the subsequent preparation with 5% fluorozirconicacid).

In one exemplary embodiment, the cationic resin-based post rinsecomposition comprises a trisaminoepoxy compound.

In certain embodiments of the methods of the present invention, afterthe substrate is contacted with the pretreatment composition and theresin-based post rinse, it is then contacted with an electrodepositablecoating composition. The electrodepositable coating compositions areeither cationic, when the post-rinse is an anionic resin-based postrinse as described above, or anionic, when the post-rinse is a cationicresin-based post rinse. In either case, the electrodepositable coatingcomposition comprises a film-forming resin.

As used herein, the term “film-forming resin” refers to resins that canform a self-supporting continuous film on at least a horizontal surfaceof a substrate upon removal of any diluents or carriers present in thecomposition or upon curing at ambient or elevated temperature.Conventional film-forming resins that may be used include, withoutlimitation, those typically used in automotive OEM coating compositions,automotive refinish coating compositions, industrial coatingcompositions, architectural coating compositions, coil coatingcompositions, and aerospace coating compositions, among others.

In certain embodiments, the coating composition comprises athermosetting film-forming resin. As used herein, the term“thermosetting” refers to resins that “set” irreversibly upon curing orcrosslinking, wherein the polymer chains of the polymeric components arejoined together by covalent bonds. This property is usually associatedwith a cross-linking reaction of the composition constituents ofteninduced, for example, by heat or radiation. Curing or crosslinkingreactions also may be carried out under ambient conditions. Once curedor crosslinked, a thermosetting resin will not melt upon the applicationof heat and is insoluble in solvents. In other embodiments, the coatingcomposition comprises a thermoplastic film-forming resin. As usedherein, the term “thermoplastic” refers to resins that comprisepolymeric components that are not joined by covalent bonds and therebycan undergo liquid flow upon heating and are soluble in solvents.

As previously indicated, in certain embodiments, the substrate iscontacted with a coating composition comprising a film-forming resin byan electrocoating step wherein an electrodepositable composition isdeposited onto the metal substrate by electrodeposition. In the processof electrodeposition, the metal substrate being treated, serving as anelectrode, and an electrically conductive counter electrode are placedin contact with an ionic, electrodepositable composition. Upon passageof an electric current between the electrode and counter electrode whilethey are in contact with the electrodepositable composition, an adherentfilm of the electrodepositable composition will deposit in asubstantially continuous manner on the metal substrate.

Electrodeposition is usually carried out at a constant voltage in therange of from 1 volt to several thousand volts, typically between 50 and500 volts. Current density is usually between 1.0 ampere and 15 amperesper square foot (10.8 to 161.5 amperes per square meter) and tends todecrease quickly during the electrodeposition process, indicatingformation of a continuous self-insulating film.

The electrodepositable composition utilized in certain embodiments ofthe present invention often comprises a resinous phase dispersed in anaqueous medium wherein the resinous phase comprises: (a) an activehydrogen group-containing ionic electrodepositable resin, and (b) acuring agent having functional groups reactive with the active hydrogengroups of (a).

In certain embodiments, the electrodepositable compositions utilized incertain embodiments of the present invention contain, as a mainfilm-forming polymer, an active hydrogen-containing ionic, oftencationic, electrodepositable resin. A wide variety of electrodepositablefilm-forming resins are known and can be used in the present inventionso long as the polymers are “water dispersible,” i.e., adapted to besolubilized, dispersed or emulsified in water. The water dispersiblepolymer is ionic in nature, that is, the polymer will contain anionicfunctional groups to impart a negative charge or, as is often preferred,cationic functional groups to impart a positive charge.

Examples of film-forming resins suitable for use in anionicelectrodepositable compositions are base-solubilized, carboxylic acidcontaining polymers, such as the reaction product or adduct of a dryingoil or semi-drying fatty acid ester with a dicarboxylic acid oranhydride; and the reaction product of a fatty acid ester, unsaturatedacid or anhydride and any additional unsaturated modifying materialswhich are further reacted with polyol. Also suitable are the at leastpartially neutralized interpolymers of hydroxy-alkyl esters ofunsaturated carboxylic acids, unsaturated carboxylic acid and at leastone other ethylenically unsaturated monomer. Still another suitableelectrodepositable film-forming resin comprises an alkyd-aminoplastvehicle, i.e., a vehicle containing an alkyd resin and an amine-aldehyderesin. Yet another anionic electrodepositable resin compositioncomprises mixed esters of a resinous polyol, such as is described inU.S. Pat. No. 3,749,657 at col. 9, lines 1 to 75 and col. 10, lines 1 to13, the cited portion of which being incorporated herein by reference.Other acid functional polymers can also be used, such as phosphatizedpolyepoxide or phosphatized acrylic polymers as are known to thoseskilled in the art.

As aforementioned, it is often desirable that the activehydrogen-containing ionic electrodepositable resin (a) is cationic andcapable of deposition on a cathode. Examples of such cationicfilm-forming resins include amine salt group-containing resins, such asthe acid-solubilized reaction products of polyepoxides and primary orsecondary amines, such as those described in U.S. Pat. Nos. 3,663,389;3,984,299; 3,947,338; and 3,947,339. Often, these amine saltgroup-containing resins are used in combination with a blockedisocyanate curing agent. The isocyanate can be fully blocked, asdescribed in U.S. Pat. No. 3,984,299, or the isocyanate can be partiallyblocked and reacted with the resin backbone, such as is described inU.S. Pat. No. 3,947,338. Also, one-component compositions as describedin U.S. Pat. No. 4,134,866 and DE-OS No. 2,707,405 can be used as thefilm-forming resin. Besides the epoxy-amine reaction products,film-forming resins can also be selected from cationic acrylic resins,such as those described in U.S. Pat. Nos. 3,455,806 and 3,928,157.

Besides amine salt group-containing resins, quaternary ammonium saltgroup-containing resins can also be employed, such as those formed fromreacting an organic polyepoxide with a tertiary amine salt as describedin U.S. Pat. Nos. 3,962,165; 3,975,346; and 4,001,101. Examples of othercationic resins are ternary sulfonium salt group-containing resins andquaternary phosphonium salt-group containing resins, such as thosedescribed in U.S. Pat. Nos. 3,793,278 and 3,984,922, respectively. Also,film-forming resins which cure via transesterification, such asdescribed in European Application No. 12463 can be used. Further,cationic compositions prepared from Mannich bases, such as described inU.S. Pat. No. 4,134,932, can be used.

In certain embodiments, the resins present in the electrodepositablecomposition are positively charged resins which contain primary and/orsecondary amine groups, such as described in U.S. Pat. Nos. 3,663,389;3,947,339; and 4,116,900. In U.S. Pat. No. 3,947,339, a polyketiminederivative of a polyamine, such as diethylenetriamine ortriethylenetetraamine, is reacted with a polyepoxide. When the reactionproduct is neutralized with acid and dispersed in water, free primaryamine groups are generated. Also, equivalent products are formed whenpolyepoxide is reacted with excess polyamines, such asdiethylenetriamine and triethylenetetraamine, and the excess polyaminevacuum stripped from the reaction mixture, as described in U.S. Pat.Nos. 3,663,389 and 4,116,900.

In certain embodiments, the active hydrogen-containing ionicelectrodepositable resin is present in the electrodepositablecomposition in an amount of 1 to 60 percent by weight, such as 5 to 25percent by weight, based on total weight of the electrodeposition bath.

As indicated, the resinous phase of the electrodepositable compositionoften further comprises a curing agent adapted to react with the activehydrogen groups of the ionic electrodepositable resin. For example, bothblocked organic polyisocyanate and aminoplast curing agents are suitablefor use in the present invention, although blocked isocyanates are oftenpreferred for cathodic electrodeposition.

Aminoplast resins, which are often the preferred curing agent foranionic electrodeposition, are the condensation products of amines oramides with aldehydes. Examples of suitable amine or amides aremelamine, benzoguanamine, urea and similar compounds. Generally, thealdehyde employed is formaldehyde, although products can be made fromother aldehydes, such as acetaldehyde and furfural. The condensationproducts contain methylol groups or similar alkylol groups depending onthe particular aldehyde employed. Often, these methylol groups areetherified by reaction with an alcohol, such as a monohydric alcoholcontaining from 1 to 4 carbon atoms, such as methanol, ethanol,isopropanol, and n-butanol. Aminoplast resins are commercially availablefrom American Cyanamid Co. under the trademark CYMEL and from MonsantoChemical Co. under the trademark RESIMENE.

The aminoplast curing agents are often utilized in conjunction with theactive hydrogen containing anionic electrodepositable resin in amountsranging from 5 percent to 60 percent by weight, such as from 20 percentto 40 percent by weight, the percentages based on the total weight ofthe resin solids in the electrodepositable composition.

As indicated, blocked organic polyisocyanates are often used as thecuring agent in cathodic electrodeposition compositions. Thepolyisocyanates can be fully blocked as described in U.S. Pat. No.3,984,299 at col. 1, lines 1 to 68, col. 2, and col. 3, lines 1 to 15,or partially blocked and reacted with the polymer backbone as describedin U.S. Pat. No. 3,947,338 at col. 2, lines 65 to 68, col. 3, and col. 4lines 1 to 30, the cited portions of which being incorporated herein byreference. By “blocked” is meant that the isocyanate groups have beenreacted with a compound so that the resultant blocked isocyanate groupis stable to active hydrogens at ambient temperature but reactive withactive hydrogens in the film forming polymer at elevated temperaturesusually between 90° C. and 200° C.

Suitable polyisocyanates include aromatic and aliphatic polyisocyanates,including cycloaliphatic polyisocyanates and representative examplesinclude diphenylmethane-4,4′-diisocyanate (MDI), 2,4- or 2,6-toluenediisocyanate (TDI), including mixtures thereof, p-phenylenediisocyanate, tetramethylene and hexamethylene diisocyanates,dicyclohexylmethane-4,4′-diisocyanate, isophorone diisocyanate, mixturesof phenylmethane-4,4′-diisocyanate and polymethylenepolyphenylisocyanate. Higher polyisocyanates, such as triisocyanates canbe used. An example would includetriphenylmethane-4,4′,4″-triisocyanate. Isocyanate ( )-prepolymers withpolyols such as neopentyl glycol and trimethylolpropane and withpolymeric polyols such as polycaprolactone diols and triols (NCO/OHequivalent ratio greater than 1) can also be used.

The polyisocyanate curing agents are typically utilized in conjunctionwith the active hydrogen containing cationic electrodepositable resin inamounts ranging from 5 percent to 60 percent by weight, such as from 20percent to 50 percent by weight, the percentages based on the totalweight of the resin solids of the electrodepositable composition.

In certain embodiments, the coating composition comprising afilm-forming resin also comprises yttrium. In certain embodiments,yttrium is present in such compositions in an amount from 10 to 10,000ppm, such as not more than 5,000 ppm, and, in some cases, not more than1,000 ppm, of total yttrium (measured as elemental yttrium).

Both soluble and insoluble yttrium compounds may serve as the source ofyttrium. Examples of yttrium sources suitable for use in lead-freeelectrodepositable coating compositions are soluble organic andinorganic yttrium salts such as yttrium acetate, yttrium chloride,yttrium formate, yttrium carbonate, yttrium sulfamate, yttrium lactateand yttrium nitrate. When the yttrium is to be added to an electrocoatbath as an aqueous solution, yttrium nitrate, a readily availableyttrium compound, is a preferred yttrium source. Other yttrium compoundssuitable for use in electrodepositable compositions are organic andinorganic yttrium compounds such as yttrium oxide, yttrium bromide,yttrium hydroxide, yttrium molybdate, yttrium sulfate, yttrium silicate,and yttrium oxalate. Organoyttrium complexes and yttrium metal can alsobe used. When the yttrium is to be incorporated into an electrocoat bathas a component in the pigment paste, yttrium oxide is often thepreferred source of yttrium.

The electrodepositable compositions described herein are in the form ofan aqueous dispersion. The term “dispersion” is believed to be atwo-phase transparent, translucent or opaque resinous system in whichthe resin is in the dispersed phase and the water is in the continuousphase. The average particle size of the resinous phase is generally lessthan 1.0 and usually less than 0.5 microns, often less than 0.15 micron.

The concentration of the resinous phase in the aqueous medium is oftenat least 1 percent by weight, such as from 2 to 60 percent by weight,based on total weight of the aqueous dispersion. When such compositionsare in the form of resin concentrates, they generally have a resinsolids content of 20 to 60 percent by weight based on weight of theaqueous dispersion.

The electrodepositable compositions described herein are often suppliedas two components: (1) a clear resin feed, which includes generally theactive hydrogen-containing ionic electrodepositable resin, i.e., themain film-forming polymer, the curing agent, and any additionalwater-dispersible, non-pigmented components; and (2) a pigment paste,which generally includes one or more pigments, a water-dispersible grindresin which can be the same or different from the main-film formingpolymer, and, optionally, additives such as wetting or dispersing aids.Electrodeposition bath components (1) and (2) are dispersed in anaqueous medium which comprises water and, usually, coalescing solvents.

As aforementioned, besides water, the aqueous medium may contain acoalescing solvent. Useful coalescing solvents are often hydrocarbons,alcohols, esters, ethers and ketones. The preferred coalescing solventsare often alcohols, polyols and ketones. Specific coalescing solventsinclude isopropanol, butanol, 2-ethylhexanol, isophorone,2-methoxypentanone, ethylene and propylene glycol and the monoethylmonobutyl and monohexyl ethers of ethylene glycol. The amount ofcoalescing solvent is generally between 0.01 and 25 percent, such asfrom 0.05 to 5 percent by weight based on total weight of the aqueousmedium.

In addition, a colorant and, if desired, various additives such assurfactants, wetting agents or catalyst can be included in the coatingcomposition comprising a film-forming resin. As used herein, the term“colorant” means any substance that imparts color and/or other opacityand/or other visual effect to the composition. The colorant can be addedto the composition in any suitable form, such as discrete particles,dispersions, solutions and/or flakes. A single colorant or a mixture oftwo or more colorants can be used.

Example colorants include pigments, dyes and tints, such as those usedin the paint industry and/or listed in the Dry Color ManufacturersAssociation (DCMA), as well as special effect compositions. A colorantmay include, for example, a finely divided solid powder that isinsoluble but wettable under the conditions of use. A colorant can beorganic or inorganic and can be agglomerated or non-agglomerated.Colorants can be incorporated by use of a grind vehicle, such as anacrylic grind vehicle, the use of which will be familiar to one skilledin the art.

Example pigments and/or pigment compositions include, but are notlimited to, carbazole dioxazine crude pigment, azo, monoazo, disazo,naphthol AS, salt type (lakes), benzimidazolone, condensation, metalcomplex, isoindolinone, isoindoline and polycyclic phthalocyanine,quinacridone, perylene, perinone, diketopyrrolo pyrrole, thioindigo,anthraquinone, indanthrone, anthrapyrimidine, flavanthrone, pyranthrone,anthanthrone, dioxazine, triarylcarbonium, quinophthalone pigments,diketo pyrrolo pyrrole red (“DPPBO red”), titanium dioxide, carbon blackand mixtures thereof. The terms “pigment” and “colored filler” can beused interchangeably.

Example dyes include, but are not limited to, those that are solventand/or aqueous based such as pthalo green or blue, iron oxide, bismuthvanadate, anthraquinone, perylene, aluminum and quinacridone.

Example tints include, but are not limited to, pigments dispersed inwater-based or water miscible carriers such as AQUA-CHEM 896commercially available from Degussa, Inc., CHARISMA COLORANTS andMAXITONER INDUSTRIAL COLORANTS commercially available from AccurateDispersions division of Eastman Chemical, Inc.

As noted above, the colorant can be in the form of a dispersionincluding, but not limited to, a nanoparticle dispersion. Nanoparticledispersions can include one or more highly dispersed nanoparticlecolorants and/or colorant particles that produce a desired visible colorand/or opacity and/or visual effect. Nanoparticle dispersions caninclude colorants such as pigments or dyes having a particle size ofless than 150 nm, such as less than 70 nm, or less than 30 nm.Nanoparticles can be produced by milling stock organic or inorganicpigments with grinding media having a particle size of less than 0.5 mmExample nanoparticle dispersions and methods for making them areidentified in U.S. Pat. No. 6,875,800 B2, which is incorporated hereinby reference. Nanoparticle dispersions can also be produced bycrystallization, precipitation, gas phase condensation, and chemicalattrition (i.e., partial dissolution). In order to minimizere-agglomeration of nanoparticles within the coating, a dispersion ofresin-coated nanoparticles can be used. As used herein, a “dispersion ofresin-coated nanoparticles” refers to a continuous phase in which isdispersed discreet “composite microparticles” that comprise ananoparticle and a resin coating on the nanoparticle. Exampledispersions of resin-coated nanoparticles and methods for making themare identified in United States Patent Application Publication2005-0287348 A1, filed Jun. 24, 2004, U.S. Provisional Application No.60/482,167 filed Jun. 24, 2003, and U.S. patent application Ser. No.11/337,062, filed Jan. 20, 2006, which is also incorporated herein byreference.

Example special effect compositions that may be used include pigmentsand/or compositions that produce one or more appearance effects such asreflectance, pearlescence, metallic sheen, phosphorescence,fluorescence, photochromism, photosensitivity, thermochromism,goniochromism and/or color-change. Additional special effectcompositions can provide other perceptible properties, such as opacityor texture. In certain embodiments, special effect compositions canproduce a color shift, such that the color of the coating changes whenthe coating is viewed at different angles. Example color effectcompositions are identified in U.S. Pat. No. 6,894,086, incorporatedherein by reference. Additional color effect compositions can includetransparent coated mica and/or synthetic mica, coated silica, coatedalumina, a transparent liquid crystal pigment, a liquid crystal coating,and/or any composition wherein interference results from a refractiveindex differential within the material and not because of the refractiveindex differential between the surface of the material and the air.

In certain embodiments, a photosensitive composition and/or photochromiccomposition, which reversibly alters its color when exposed to one ormore light sources, can be used in the present invention. Photochromicand/or photosensitive compositions can be activated by exposure toradiation of a specified wavelength. When the composition becomesexcited, the molecular structure is changed and the altered structureexhibits a new color that is different from the original color of thecomposition. When the exposure to radiation is removed, the photochromicand/or photosensitive composition can return to a state of rest, inwhich the original color of the composition returns. In certainembodiments, the photochromic and/or photosensitive composition can becolorless in a non-excited state and exhibit a color in an excitedstate. Full color-change can appear within milliseconds to severalminutes, such as from 20 seconds to 60 seconds. Example photochromicand/or photosensitive compositions include photochromic dyes.

In certain embodiments, the photosensitive composition and/orphotochromic composition can be associated with and/or at leastpartially bound to, such as by covalent bonding, a polymer and/orpolymeric materials of a polymerizable component. In contrast to somecoatings in which the photosensitive composition may migrate out of thecoating and crystallize into the substrate, the photosensitivecomposition and/or photochromic composition associated with and/or atleast partially bound to a polymer and/or polymerizable component inaccordance with certain embodiments of the present invention, haveminimal migration out of the coating. Example photosensitivecompositions and/or photochromic compositions and methods for makingthem are identified in U.S. application Ser. No. 10/892,919 filed Jul.16, 2004, incorporated herein by reference.

In general, the colorant can be present in the coating composition inany amount sufficient to impart the desired visual and/or color effect.The colorant may comprise from 1 to 65 weight percent, such as from 3 to40 weight percent or 5 to 35 weight percent, with weight percent basedon the total weight of the compositions.

After deposition, the coating is often heated to cure the depositedcomposition. The heating or curing operation is often carried out at atemperature in the range of from 120 to 250° C., such as from 120 to190° C. for a period of time ranging from 10 to 60 minutes. In certainembodiments, the thickness of the resultant film is from 10 to 50microns.

As will be appreciated by the foregoing description, the presentinvention is directed to methods for coating a metal substratecomprising: (a) contacting the substrate with a pretreatment compositioncomprising a group IIIB metal and/or a group IVB metal, (b) contactingthe substrate with a resin-based post rinse composition that compriseseither an anionic or cationic resin-based post rinse composition, (c)electrophoretically depositing either an anionic or cationicelectrodepositable coating composition onto the substrate, wherein ananionic electrodepositable coating composition is utilized inconjunction with the cationic resin-based post rinse composition andwherein a cationic electrodepositable coating composition is utilized inconjunction with the anionic resin-based post rinse composition .

In certain embodiments, the three steps (a), (b) and (c) are donesequentially without any intervening steps or processes. In certainother embodiments, one or more intervening steps or processes may occurbetween any of steps (a), (b) and/or (c).

In certain embodiments, step (b) occurs immediately after step (a), andin certain other embodiments step (c) occurs immediately after step (b)and/or after step (a). In still other embodiments, step (c) occursimmediately after step (b) which itself occurs immediately after step(a).

These methods of the present invention do not include depositing a zincphosphate or chromate-containing coating on the substrate.

As has been indicated throughout the foregoing description, the methodsand coated substrates of the present invention, in certain embodiments,do not include the deposition of a heavy metal phosphate, such as zincphosphate, or a chromate. As a result, the environmental drawbacksassociated with such materials is avoided. Nevertheless, the methods ofthe present invention have been shown to provide coated substrates thatare, in at least some cases, resistant to corrosion at a levelcomparable to, in some cases even superior to (as illustrated in theExamples), methods wherein such materials are used. This is a surprisingand unexpected discovery of the present invention and satisfies a longfelt need in the art. In addition, the methods of the present inventionhave been shown to avoid the discoloration of subsequently appliedcoatings, such as certain non-black electrodeposited coatings.

Illustrating the invention are the following examples that are not to beconsidered as limiting the invention to their details. All parts andpercentages in the examples, as well as throughout the specification,are by weight unless otherwise indicated.

EXAMPLE 1

Coating compositions were prepared as follows:

-   -   Cleaner 1: Chemkleen 166 HP/171ALF, alkaline cleaner,        commercially available from PPG Industries, Inc.    -   Pretreatment 1: CHEMFOS 700/CHEMSEAL 59, immersion applied        tricationic Zn phosphate and sealer, commercially available from        PPG Industries, Inc.    -   Pretreatment 2: ZIRCOBOND®, immersion applied zirconium        pretreatment, commercially available from PPG Industries, Inc.    -   Post Rinse 1: Resin containing post rinse zirconium pretreatment        based on a phosphatized (anionic) epoxy polymer in an aqueous        solution is prepared by dissolving 2% (w/w) Nupal® 510R        (commercially available from PPG Industries, Inc.) in 5 gal of        H₂O, with a pH=3.    -   Post Rinse 2: Resin containing post rinse zirconium pretreatment        based on a phosphatized (anionic) epoxy polymer in an aqueous        solution is prepared by dissolving 2% (w/w) Nupal® 435F        (commercially available from PPG Industries, Inc.) in 5 gal of        H₂O, with a pH=3.    -   Post Rinse 3: Resin containing post rinse zirconium pretreatment        based on an amine adduct of EPON 828 (cationic) polymer in an        aqueous solution prepared by dissolving 2% (w/w) amine adduct of        EPON 828 in 5 gal of H₂O, with a pH=10.4.    -   Post Rinse 4: Resin containing dry-in-place coating for a        zirconium pretreatment based on a phosphatized (anionic) epoxy        polymer in an aqueous solution prepared by dissolving 0.1% (w/w)        Nupal® 510R (commercially available from PPG Industries, Inc.)        in 5 gal of H₂O, with a pH=4.    -   Post Rinse 5: Deionized water post rinse.    -   Paint 1: ED6060CZ, a cathodic electrocoat commercially available        from PPG Industries.    -   Paint 2: AEROCRON CF, an anionic electrocoat commercially        available from PPG Industries.

Example 1 Evaluation of Throwpower of Anionic or CationicElectrodepositable Coating Composition for Various Pretreatment/PostRinse Systems

In this example, Post Rinses 1-5 were evaluated to determine thethrowpower of subsequently applied anionic or cationicelectrodepositable coatings.

In this test, the panels were prepared as follows:

Step 1: Cleaning and Pretreatment

The coating systems were cleaned using Cleaner 1, rinsed with deionizedwater, and pretreated at 27° C. in with either Pretreatment 1 orPretreatment 2 for 2 minutes. The panels were then rinsed with deionizedwater.

Step 2: Application of Post Rinse

Next, for Post Rinses 1-3 and 5, respectively, the panels were immersedin the post rinse solution for 1 minute and rinsed with deionized water.The panels were then dried by for 5 minutes at 55 ° C. using forced air.

For Post Rinse 4, the cleaned and pretreated panels were misted (i.e.coated) with Post Rinse 4. The panels were then dried by for 5 minutesat 55 ° C. using forced air.

Step 3: Application of Electrodepositable Coating Composition

Next, two 4×12″ pretreated and post-rinsed panels as prepared in Steps 1and 2 above are placed on either side of a 4 mm shim and clampedtogether. The shimmed panels are immersed 27 cm into the electrocoatbath (either Paint 1 or Paint 2) and coated as described below.Throwpower readings are recorded as a percentage by measuring thedistance (in cm) from the bottom of the back side of the panels to thepoint where no coating was deposited and dividing that number by 27 cm.

Paint 1 was electrophoretically applied to the panels at 0.0008-0.0010inches and cured for 25 minutes at 175° C. in an electric oven.

Paint 2 was electrophoretically applied to the panels at 0.0008-0.0010inches and cured for 30 minutes at 93° C. in an electric oven.

The results are shown in Table 1 below:

TABLE 1 Throwpower Performance Paint 1, % Paint 2, % Pretreatment/PostRinse Throwpower Throwpower Pretreatment 1/Post Rinse 5 69 34Pretreatment 2/Post Rinse 1 67 32 Pretreatment 2/Post Rinse 2 66 32Pretreatment 2/Post Rinse 3 55 38 Pretreatment 2/Post Rinse 4 67 31Pretreatment 2/Post Rinse 5 56 30

As Table 1 confirms, the anionic post rinse compositions of the presentinvention (Post Rinses 1, 2 and 4) applied after Pretreatment 2 providedincreased throwpower for a subsequently applied cationicelectrodepositable coating composition (Paint 1) as compared to adeionized water post rinse (Post Rinse 5) and had comparable throwpowerto a zinc phosphate pretreatment system (Pretreatment 1 with Post Rinse5). The table also confirms that the application of an cationic postrinse composition (Post Rinse 3) followed by the deposition of thecationic electrodepositable coating composition (Paint 2) had virtuallyno effect on throwpower as compared to a deionized water post rinse(Post Rinse 5).

In addition, the catonic post rinse compositions of the presentinvention (Post Rinse 3) provided increased throwpower for asubsequently applied anionic electrodepositable coating composition(Paint 2) as compared to a deionized water post rinse (Post Rinse 5) andincreased throwpower to a zinc phosphate pretreatment system(Pretreatment 1 with Post Rinse 5). The table also confirms that theapplication of an anionic post rinse composition (Post Rinses 1, 2 and4) followed by the deposition of the anionic electrodepositable coatingcomposition had virtually no effect on throwpower as compared to adeionized water post rinse (Post Rinse 5).

Example 2 Evaluation of Corrosion Performance of Anionic or CationicElectrodepositable Coating Composition for Various Pretreatment/PostRinse Systems

In this example, the electrodeposited panels of Example 1 were alsoevaluated for corrosion performance. The test procedure was performedusing 40 cycles of GM-9511P and measuring the. The results are shown inTable 2.

TABLE 2 Corrosion Performance - GM9511P 40 cycles, mm Pretreatment/PostRinse Paint 1 Paint 2 Pretreatment 1/Post Rinse 5 5.5 2.7 Pretreatment2/Post Rinse 1 7.6 6.4 Pretreatment 2/Post Rinse 2 8.1 9.7 Pretreatment2/Post Rinse 3 7.3 7.9 Pretreatment 2/Post Rinse 4 9.4 8.2 Pretreatment2/Post Rinse 5 8.2 8.0

As Table 2 confirms, the anionic post rinse compositions of the presentinvention (Post Rinses 1, 2 and 4) applied after Pretreatment 2 providedcomparable corrosion resistance for a subsequently applied cationicelectrodepositable coating composition (Paint 1) as compared to adeionized water post rinse (Post Rinse 5).

In addition, the catonic post rinse compositions of the presentinvention (Post Rinse 3) provided comparable corrosion resistance for asubsequently applied anionic electrodepositable coating composition(Paint 2) as compared to a deionized water post rinse (Post Rinse 5).

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications which are within the spirit and scopeof the invention, as defined by the appended claims.

We claim:
 1. A method for coating a substrate comprising: (a) contactingthe substrate with a pretreatment solution comprising a group IIIBand/or a group IVB metal and an electropositive metal; (b) contactingthe substrate with an cationic resin-based post rinse compositioncomprising a cationic resin; and (c) electrophoretically depositing ananionic electrodepositable coating composition onto the substrate. 2.The method of claim 1, wherein said cationic resin comprises atrisaminoepoxy resin.
 3. The method of claim 1, wherein step (a) occursbefore step (b) and wherein step (b) occurs before step (c).
 4. Themethod of claim 1, wherein said group IVB metal comprises zirconium. 5.The method of claim 1, wherein said group IIIB metal and/or group IVBmetal comprises a group IIIB metal compound and/or a group IVB metalcompound.
 6. The method of claim 5, wherein said group IVB metalcompound comprises a zirconium compound
 7. The method of claim 1,wherein step (b) comprises: immersing the substrate in a bath comprisingthe cationic resin-based post rinse composition; removing the substratefrom said bath; and rinsing the substrate with water.
 8. The method ofclaim 1, wherein the throwpower of the anionic electrodepositablecoating composition is increased by at least 6% compared to thethrowpower of said anionic electrodepositable coating compositionapplied to the substrate without step (b).
 9. The method of claim 1,wherein said cationic resin comprises an amine adduct of an epoxy resin.10. A coated substrate coated according to the method of claim 1.